Processes for the production of an alkyl acrylate by the reaction of an alkyl alcohol with acrylic acid in the presence of an esterification catalysts are well known. To provide improvements in these processes without the use of new esterification catalysts, are unusual and unique.
In the known esterification processes, the acrylic acid used normally contains inhibitors which prevent undesired polymerization prior to use. The inhibitors commonly used are phenothiazine, methylene blue, phenolic type inhibitors such as hydroquinone, p-methoxyphenols and the like. It is not generally known to use a metal additive in combination with organic inhibitors in acrylic acid. In Chemical Abstracts Vol. 74,1971, 112642V, a Japanese patent (70-35,285) filed June 1, 1967, assigned to Nippon Kayaku, Co. Ltd., describes the mixture of chromium acetate with hydroquinone as a satisfactory inhibitor for acrylic acid and methacrylic acid. In Japanese Patent Publication No. 51-98211, filed Feb. 15, 1975 assigned to Sumitomo Chemical Co. Ltd., the combination of a manganese salt and phenolic type inhibitors provided satisfactory stabilization of acrylic acid. In copending application entitled "Stabilized Ethylenically Unsaturated Organic Compounds" Ser. No. 510,870, filed July 5, 1983 and assigned to the same assignee as the present application, describes the use of cerium in combination with other inhibitors as an inhibitor for polymerizable ethylenically unsaturated organic compounds. In copending application entitled "Improved Process for Production of Ethyl Acrylate" Ser. No. 06/510,846 filed July 5, 1983 assigned to the same assignee as the present application, there is described an improved process in the production of ethyl acrylate by the reaction of ethylene and acrylic acid containing polymerization inhibitors especially phenolic type polymerization inhibitors in the presence of sulfuric acid and in the presence of manganese or cerium metal ions soluble in the reaction mixture. Improved efficiencies of ethyl acrylate production from acrylic acid are achieved using this procedure. In this invention, improvements have been achieved in an esterification reaction of an alkyl alcohol and acrylic acid containing phenolic type inhibitors to produce an alkyl acrylate in the presence of manganese or cerium metal ions soluble in the reaction mixture.